Telephone-exchange system.



E. E. CLEMENT. TELEPHONE EXGHANGE SYSTEM. APPLICATION FILED MAR. 17, 1905. RENEWED JULY 2, 1909.

1,@36,961, v Patented Au .27,.1912. f

4 SHEETS-SHEET 1.

B. E. CLEMENT. TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED MAR. 17, 1905v RENEWED JULY 2, 1909.

1,036,961, Patented Aug. 27, 1912.

4 SHEETS-SHEET z. m 6

E. E. CLEMENT. TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED MAR.17, 1905. RENEWED JULY 2, 1909;

1 ,O36,96 1 o Patented Aug. 27, 1912.

4 SHEETS-S 9 E IJIJIIMHE Inventor WIIIIGQQEB B. E. CLEMENT. TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED MAR.17, 1905v RENEWED JULY 2, 1909.

1,036,961, Patented Aug.27, 1912.

4 SHBETB-BHEET 4.

Q IIIIIIIIIIHIIH Inventor nnrrnn srarns 'ra'rnn'r @Fhltllt.

EDWARD 1E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO THE NORTH ELECTRIG'COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

TELEPHONE-EXCHANGE SYSTEM.

Loseeei.

Specification of Letters Yatent.

Application filed March 17, 1905, Serial No.'250,634. Renewed July 2, 1909. Serial No. 5053525.

To all whom it may concern:

Be it known that I, EDWARD E. CLEMENT,

a citizen of the United States, residing at Washington, in the District of Columbia,

have invented certain new and useful. Im-

provements in Telephone-Exchange Systems, of which the following is a specification, reference being had therein to the accompanying drawing. 7

My invention relates to telephone exchange systems and has for its object the improvement of such systems by the combination in-op'eration of the best features of so-called manualsystems with the best features of the so-called automatic systems.

According to past practice, prior to my invention, the best and most widely used form of manual system has been that known as the straight multiple, wherein the switchboard or boards forthe interconnection of subscribers have been provided with an I answering jack for each line, and with multiple jacks for all the lines duplicated upon each section or within reach of each opera-' tor. ,The number of multiple jacks in such a system is very large'inp-ro-portion to the number of lines, and in a large exchange serving many subscribers gives rise to many ditliculties,mechanical, electrical, and financial. On the other hand, the best and most widely known form of automatic system has been one provided with an automatic switch or. first selector for each line, and auxiliary switches controlled bythe first selector switches, some or all of which have been provided with multiple contacts for the Various subscribers lines.

The most expensive and generally ob ec- I tionablepart of a multiple manual system is that embodied in the multiple-jacks. The

'. which is required of them in the regular manual system, can handle a great many more lines per operator, so that only a few opelntors are rq I .efiect Very large.

nary first selector switch.

savings by this arrangement, as well as a positive gain in etliciency, and many incidental advantages which will sufliciently appear from the following description.

Briefly stated,-my invention comprehends 'a manual switchboard or boards provided with a line terminal and calling signal for each line, and cord circuits whereby the operators may answer the subscribers calls by plugging them through to the regular first or other selector switches. The subscribers are provided with the regular automatic sender or transmitter, and so far as they areconcerned the system is full automatic. The operators have substantially nothing ,to do but stick plugs, and as the number of automatic switches required is only about thirty per cent. of the number in the full automatic systems, the chances of trouble, and the difficulties usually met in locating the same are correspondingly;

reduced. I

My invention is illustrated in the accompanying drawings, wherein Figure 1 shows a subscribers station and a, portion of the central ofiice circuits, in cluding an operator s cord circuit. is a diagram of successive link conductors and switches in the automatic portion of the system. Fig. 3 is a diagram similar to Fig. 1, showing a modification; and Fig. l is a diagram of a further preferred modification.

Referring to Figs. 1 and 2, I have shown the simplest conception of my invention as applied to the Strowger automatic system; Between the dotted lines 100 and 200, Fig. 1, I have shown interposed the necessary apparatus to form the connecting link between the subscribersstation and the ordi- This apparatus does not change the operatic-11 of the rest of the system, which remains the same throughout. This interposed consists of a line jack and an annunciator drop at which the subsoribers line terminates, the trunk jaclr and busy lamp to which the first connector switch is .terminated and the cord-circuit used to connect the line-jack with thetrunk-jack and thus complete the circuit. At the subscribefls station Av the regular 'Strowger instrument is shown, 1n additionto which is addeda apparatus v hand generator G. The line-wires 1 and 2 terminate in the central office on the jack" J. To the inner'contact 7' and to the wire 1 there is connected the annunciator-drop M, and to contact j there are connected private normal multiples leading to the connector switches. The contact j" is grounded. The cord-circuit consists of the answering-plug P, with a tip 22 normally connected to generator G, through the contacts M, 70 with 10 the latch magnet Sin series. The tip pof the calling-plug P is connected to the inner contact k Thesleeve p of the answeringplug 7) is connected to the opposite'side of v, the generator G, throughthe contacts is 15 and 70 The sleeve 79 of P is connected to the contact 70.. ..These contacts are con trolled by the latch s of the magnet S. The third conductor p of the calling-plug. P is grounded. The first selector-switch is connected to the springs. 7' and 7'? of the trunk-jack J by the wires 10 and 11. The busy lamps s are connected to battery B by the wire 13.

selector switch Z and the connector switch Z being of the. Well known Strowger type and no partof my present invention,I will not describe them indetail. The first selector switchZ has a vertical relay S, a rotary relay S a yertical magnets, a rotary magnet 8, a back release' relay X, a private relay S ah'dLa release magnet W. trunk wipers '2' an dfa and the private wiper 2 are mounted on the spindle a, The second selector 'Z"Fig. 2, consists of the vertical relay S", rotary relay S vertical 'magnet s, rotary magnet 3 back release relay X, private relay S{, and the release magnetVV. The trunk wipers 2L and 2 and the private wiper 2 are mounted on the spindle a; v

' The connectorswitch Z Fig. 2, consists of the vertical relay S rotary relay S vertical magnet s, rotary magnet a, private relay 8, back signal relays W W, ringing relay Y and release magnet W The trunk wipers a and a and the private wiper a are mounted on the spindle 2".-

The wires 18 and' 20, 19 and 21 are separated by the condensersC and C,respectively. These switches'are shown in patents issued March'13, 1906, 'to'Ke'ith and Erickson Nos. 815,176 and 815,321.

lows: The subscriber'signals by turning his hand generator G, which throws the drop annunciato'r M at the centraloific'e through the contacts j 9'. The operator' perceiving the signalinserts' the answering-plug P into trunk jack J which does not show azbusy I signal, preferably the latter first. "This opens the contacts j, 7?, disconnects the line-- annunciatorM, also grounds private'normalmultiple. As soon as thls' connection; is

y The first selector switch the second- The operation ofjthis system is as fol the jack J, "and the calling pluglP 1I llZ 0 any made, generator current is sent outon the subscribers line with the'relay S, in series. The armature s is then attracted and releases the latch s. This release disconnects the generator G by breaking the contact is, kt and I0 and at the same time 'closes the contacts 70,70 and 76 7c. The tip 31 of the answering-plug P, and the tip p of the calling plug P are now connected as are the sleeve 12" of the answering-plug P and the sleeve p of the calling-plug P. This completes the connection between the subscribers instrument;and the the line, these makes and breaks correspond ing to the thousands numeralof the number with which he desires to be connected. These makes and breaks or impulses actuate the vertical relay S in the'first selectorv switch Z, by way of line-wire -1, strands 6 and '8 in the cord-circuit, wire 1.0, leading to the trunk-jack J. After the last impulse has come in over the vertical side of the line, one impulse is sent in overthe rotary side of the line andmoves the side switch one step, which cuts on the rotary magnet s.

The actuating of this relay, S causes the spindle Z, carrying thewipers, to step up to the desired'row. Therotary magnet 8 now being. cut on, the spindle Z begins to rotate and continues to rotate. until the wiper 2 finds a contact in the private normal which has no ground, that is to say not busy. At the first step of the side switch, the private relay S is placedin connection 'with wiper 2 with the relay X, in series This relay. S continues to hold up so long as 'the wipers finds a' grounded contact.

The instant a fre e'contact is found, that is an idle 'one, the relay S becomes denergized, causing the side switch to make a second" step which cuts off the rotary mag nets 8 grounds the wiper a through the windings of relay X, disconnects the'vertical and rotary relays S and S and 'conmeets the trunk-wires l0 and 11 to the wires 12 and 13, leading tothe wipers a and 2 *lhe' subscribers' stationis now inconnection with the-contacts leading to "the thousand group ofv the party he desires to be connected with. The second movement of, his dial sending in impulses over the vertical side. ofthe line corresponding-to the hundred 'num'eral'of the party hcwishes to be connected with, actuates the vertical relay S of the second selector switch .Z, Fig. 2.

After the last impulse has come in over i the vertical side of the line, one impulse is the spindle 2, carrying the wipers, to step- 2 finds an idle contact.

up to the desired row. The rotary magnet 8 being cut-on,- the spindle now. begins to rotate and continues to rotate until the wiper The private relay S connected to the wiper 2 through the relay X, in series, continues to attract its armature cutting ott the vertical magnet s so long as the wiper z finds a busy or grounded contact. The instant it finds an idle contact the relay S" becomes de'einer gized. This causes the side switch to make one more step, which cuts oil the rotary magnet 8 grounds the wiper a" through the winding of relay X, disconnects the vertical and rotary relays S and S and connects the trunk-wires 14 and 15 to the wires 16 and 17, respectively, leading to the wipers z and a. The relay X of the first selector switch Z and the relay X" of the second selector switch Z are low-wound and will not operate in series with the relays S and S respectively. The subscriber is now connected over the vertical side of the line by the line 1, strands 6 and 8 of the cordcircuit, wires 10 and 12 and wiper 2, selector sivitch Z, wires 14; and 16 to the wiper 2 -of the second selector switch Z, -0ver the number of the ten numeral wanted, coming in 7 over the vertical side of the line actuate the vertical relay S, which in turn operates the vertical magnet s and causes the spindle carrying the wipers to step up to the desired row. After the last impulse has come in over the vertical side of the line, one im'pulsel is sent in over the rotary side oft-he line, which makes the side switch take one step. This cuts off the vertical magnet 8 through the normally closed contacts of the private relay S. It also connects the release magnet W to the wiper a, through the normal y open contacts of the private relay S The subscriber is now-connected to contacts leading to the ten group of the line'he desires.

The fourth and last movement of his dialf sends in impulses over the vertical side of the line corresponding to the unit of the line he wishes to be connected with. These impulses actuate the vertical relay" 8, which in turn operates the rotary magnet 8 through the normally closed contacts of relay S ing the wipers, to rotate and places the This causes the. spindle e carry- Wipers 2 and 2 in connection with the line desired. Atter the lastimpulse has come in over the vertical side of the line, one impulse comes in over the rotary side of the line, which causes the side switch of the connectorswitch'Z to make one more step. This cuts off the rotaryv magnet s and connects the ringing relay Yin its place, grounds the wiper e and closes wires 22 and 24 to the wiper z and wires 23 andv 25 to the wiper 2 The calling-subscriber is now connected straight through to the line of the party called for. He now pushes his ringing button which places a ground on the vertical side of the line. This operates the relay S", which in turn operates the ringing relay Y through the normally closed contacts of the relay S. The relay Y while energized for ringing, disconnects the wires 20, 22, 21 and 23 to prevent generator current flowin back to the calling .subscribers station. t the end of the conversation, the subscriber in hanging up his telephone places a passing ground on both sidesof the line simultaneously, which causes the relays S p in the connector switch Z Fig. 2, to become energized and attract their armatures at the same time. This places the windings of the release magnet W and the back release magnet X, in series, one terminal of the winding X being grounded and one terminal of the windmg of magnet W being connected tobat-tery. Both'relays Will thereu on become energized, the release magnet restoring all the parts-of the connector switch Z to their normal. position, the relay X closing the circuit of the release magnet W and the back release magnet X, in series.

The magnet WV restores all the parts of the second selector switch Z to their, normal posit-ion. The back release relay X closes the circuit of the release magnet W, by way of 30, 31, 32, 33, 3st, to battery, the magnet becomes energized and in turn restores all the parts of the first selector switch Z, Fig. 1, to their normal position. The calling subscriber in addition to hanging up his telephone at the end of the conversation must turn his hand generator, which throws the clearing-out drop connected across the strands" '8 and '9 of the cord-circuit, a condenser being in series so as not to interfere with the impulses necessary in operating the selector and connector'switches- The operator upon getting this disconnect signal withdraws both plugs, which extinguishes the busy lamp s'- and its multiple in each position. The latch s is restored to its normal position, which bridges the generator across the answering-plug P ready to be used for the next-call.

Relays NV and V are extra release relays controlled by the called subscriber, in order to prevent the possibility of'soine one calling him and then maliciously keeping his this system. In Fig, 4, I have gone a. step line busy against his will. When the called subscriber hangs up his receiver he mo mentarily grounds both wires 20 and 21. energizing both relays W and W, and thereby closing the circuit of release mag net W v I In Fig. 3, I have shown a modification of farther and have shown the system in operation with a common battery for signaling purposes and a local battery for talking. The first selector switch Z, Fig. 1, and the second selector switch Z and connector switch Z Fig. 2, are used in connection with systems shown in Figs. 8 and 4 and are ,not'duplicated, as their action is the same in connection with each system. The modification in Fig, 3 consists of having acutofi relay in the line-circuit to disconnect the line-drop, instead of dependingupon breaking the contacts in the j acks. A'supervisory.

, Strowger instrument, to which in addition I leadin .to theother apparatus. there is added a hand generator G. The line-wires land 2- leadin from station A terminate in the central 0 ce injacks J. The line apparatus at (zentral consistsof the drop orannunciator M connected to the line through the'front contacts n and n of the cut-off relay N.- The cut-ofi relay N is connected to the ring 7" of'the jack J. To the ring 7' there is also connected the private normal multiple f to the automatic switches. The

"'cord:c 1rcuit consists of the answering-plu Pwith the tip 7) connected to the tip p o the calling-plug P by the strand 3 through the contact sprin 's is, k of the ringing key K. 'Thesleeve p of the answering plugP v ,'is connected'to the sleeve 72 of the callingplug P by the strand 4, through the contacts k and k of the ringing key K. The

' windings of the relays S, :S respectively, are connected to'the strands 3 and l and to battery B by the wire 7; To the third con- 'ductorp of the answering-plug-P is connected the relays to ground. A looking or 1 supervisory relay S of which one terminal of the winding is connected to battery and the other terminal to the contact a of the relay S controls the lamp 8 and is itself in turn controlled jointly by the relays S and S. The generator I is connectedto the back contacts k and k of the ringing key K. The third conductor 7) of the calling plug P is grounded. The first selector is connected to the jack J multipled in each position by the wires 10 and 11. These jacks have an associate busy lamp 8 controlled by the relay S", which is connected to the ring j of the jack J.

The operation of my system is as follows: The subscriber signals by turning his hand generator G, which throws the drop M at the'central oflice' through the contacts 11, and n of the cut-off relay N. The operator perceiving the signal inserts the answering, plug 'P into the jack J. Current then passes through the windings of the cut-off relay N and the relay S which causes their armatures to attract. This cut-off relay N disconnects the drop M, and the vrelay S places ground on the back contact .3 of the I relay S Ground isalso placed-on the private normal multiple f, which makes it busy for outgoing calls. The operator instead of asking 'for'the numberinserts the callingplug P into any trunk-jack J which does not show a busy signal. The insertion of vthe calling-plug P into the trunk-jack causes current toflow through the relay S. Therelay S then attracts its armature 3.11(I lights-thela-mp s and its multiple ln'each position, which serves as a busy signal for the other operators. Immediately after the completion of this connection, generator current or a busy back signal of some description is sent backover the calling line by the contacts is, k of the ringing key K coming into contact with the generator terminals k and is, either automatically or by the operator moving the lever. The'generator current is prevented flowing over the callingplug P by the breaking of the contacts k and k. The subscriber upon receiving the back signal knows that the connection is completed and thereupon moves his dial in the regular manner and gets his party by way of the cord-circuit and through the trunk to the selector and connector switches in the regular manner. The relays S and S are in parallel with-the vertical and rotary relays in the automatic switches, and while they respond tofthe impulses of the transmitter at the subscribers instrument, they "do not interfere with the working. of these automatic switches. At the end of the conyersatio-n, the subscriber hanging up his telephone places a. passing ground on each side of the line simultaneously. This restores the automatic switches to their nor 'mal position. This1pa'ssing ground also nosaeei causes current to flow through the two relays S and S at the same instant, which attracts their armatures. The attraction of these armatures at the same time passes current through the relay S which has its winding in series with the contacts 8 and- 8 of the relays S and S to battery. .The relay S then attracts its armature, lights the supervisory lamp .9 and remains locked through the contact 8", on which ground is placed by the-relay S The operator upon receiving the disconnect signal withdraws bot-h plugs, relay S being disconnected, its

armature falls back, removes the ground,

from the contact 3 and releases the relay S which in turn extinguishes the lamp 8. The relay S also being disconnected, extinguishes the lamp 8 and its multiple in each pos1tion.

Referring now to Fig. 4, a central signal system is shown, that is, the common battery -is used for signaling purposes and local bat.

tery used at the subscribers station for talking. At the subscribers station is shown the regular Strowger instrument, which in addi tion to the otherapparatus has a condenser C placed in'series with the ringer. There is also'a lock-out relay F. This relay is for the purpose of preventing the subscriber from using his dial until the connection has beencompleted or the signalanswered at the central o-fiice. To fulfil the first condition, that is to prevent the subscriber from operating his dial until the full connection is completed, the locking-relay F would have 'its armature. f provided with a-two-step escapement. The first stepwould be made when the operator inserted the answer-ingplug and connected the generator across the line. The second step would be made when the. connection was completed and the generator' current disconnected. -To provide for the second condition and have the armature f make but one step, thedial would be released when the operator first answered and the connection must be completed before the subscriber has time to operate his dial. The line-wires 1 and 2 leading from the subscribers station terminate in the central oflice and jack J. The line apparatus at central consists of the line-re1ay,M which controls the lamp m and is connected to the line through the contacts n, 'n, andn, n of the cut-o relay N. The relay N is connected to the ring' 7' of the jack J. The private normal multiples f are also connected to the ring j. The cord-circuitconsists of the answering-plug P, with a tip p 'co'nnectedto the tipof the calling plug P by the strand -3 through the contacts a and s" of relay S The sleeve 7; of the answering-plug P is connected to the sleeve 12' of the calling-plug P by the strand 4:, throu h the contacts 8 and a of the relay S T e windings ofthe relays S and S, respec-' regular order.

tively, are connected to therstrands 3 and at and to battery by the wire7. The relay S is connected to the third conductor of the answering-plug P by the wire 10, contacts s s and the Wire 9. One terminal of the winding-of the rekiy S- is connected to the third conductor 32 of the calling-plug P, the other terminal being grounded. A locking or supervisory relay S? is controlled jointly by the relays S and S, one terminal of the winding being connected to battery and theother in series with the contacts 8 and s. The supervisory lamp 8 is con trolled jointly by the relays S and S The operation of my system isas follows: The subscriber signals by removing his tele phone which closes the circuit of the linerelay M through the contacts 11, n, n and n of the cut-off relay which then attracts its armature, closes the contacts m and m and lights the line lamp m. The operator perceiving the signal inserts the answeringplug P into the jack J, which causes current to flow through the windings of the cut-oh relay N and the relay S in series, which causes their armatures to attractl The relay N disconnects the line-relay M, which in turn extinguishes the line-lamp m. The relay S attracting itsarmatures places generator current across the answering-plug P to the contacts 8 3*, s and s. It will be .noticed that the winding of the relay S is connected to the third conductor 79 of the answering-plug P, through the contacts 3 and s of the relay S The operator at once inserts the calling-plug P into atrunkjaclr J ,,which does not show a busy signal. The insertion of this plug causes current to flow through the windings of the relays S fit? and S in series, causing their armatures to attract. The relay Sf attracting its armature causes the busy lamp 8? and its multiple in each position to glow. The relay S at tracting its armature, disconnects the relay Sby breaking the contacts .9 and .8 The ing-plugP" into the jack J, the generator was disconnected from the answering-plug P. The subscriber is then at liberty to operate his dial. He operates his dial'in the regular manner and. gets hlS party by way of .the cord-circuit and through the trunk to the selector and connector switches in the Fig. 3-are in parallel with the vertical and rotary relays, and while they respond to ground I The relays S and S as in.

the impulses of the transmitter at the-sub scribers instrument they do not interfere with the workings of these automatic switches. At the end ofthe-conversation, as before described, a passing ground is placed on both sides of the line simultaneously, when the subscriber hangs up his telephone. This" restores the automatic switches to their normal position. This passin ground also causes current. to flow through the two relays S and S at the same instant, which attracts their armatures, The attraction of these armatures at the .--same time passes current through the relay S",- which has its winding in series with'the contacts s and s v of the relays S and S" to battery. The relay, S thenv attracts its armatures, lights the supervisory lamp '8 and remains locked through the contacts 8 208 8, 8 and s to ground.- The operator upon receiving the disconnect signal withdraws'both plugs, the relay S being disconnected, its armature falls back, removes the ground from the contact 8 of the relays" which thereupon releases and extinguish'es the lamp being disconnected. extinguishes the lamp '8 and its multiple in each position. The cut-off relay N being disconnected lets its armatures fall back and again connects the line-relay M across the line-wires 1 and 2.

Having thus described my invention, .what I claim and desire to secure by Letters Patent is:

1. In a telephone exchange system a plurality of subscribers lines, a number of first selector switches less than the number of subscribers lines, means manually controlled for bringing said first selector switches into connection with calling lines, together with means whereby the said selector switches may then be controlled by the subscribers to'select the lines wanted, and to restore the switches after use, and signal devices connected with the manual portion of the apparatus to indicate to'the operators the necessity for connection and disconnection, substantially as described.

2. In a telephone exchange system a plurality of subscribers lines, a number of first selector switches less than the number of subscribers lines, operators cord-circuits for connecting said first selector switches v with the callinglinstogether with sending \5'5 devices,-at the substations; and responsive devices at the central 'station whereby the said selector switches may then be controlled by the subscribers toselect the lineswa'nted, and "to restore the switches after use, lineannunciators and clearing-out annunciators connected with the lines and cords, respec tively, to indicate to the operators the desire of the respective subscribers for connection and disconnection, substantially as de- 6 5 scribed.

The relay S 3. In a telephone exchange system a plurality of subscribers lines terminating upon spring-jacks, a line-signal associated with each jack and controlled from the subscribers station, a plurality of first selector switches less in number than the number of lines, operators connective circuits with answering plugs and means to connect a calling line therethrough with-anidle first selector switch, a clearing-out signal associated with said answering plug, auxiliary switches containing line-terminals and cooperating with the first selector switches, and sending devices at the subscribers stations whereby after, a connection is manually initiated in response to a call, the calling subscriber may thereafter complete the connection. through the automatic switches and at the end of the conversation may restore the'same, substantially as described. '35

4. In a telephone exchange system a plurality of subscribers lines terminating at a manual switchboard, with associated sighal deviceswherebyfa calling line may attract the attention of an operator, a-number of first-selector automatic switches less than the number of lines, auxiliary switches asso. ciated therewith and contalning multipleterminals for the lines, operatorsconnective means and terminal devices 'for theselector switch circuits upon the manual switchboard manually controlled to .connect a calling line with an' idle first selector switch, means thereaften'controlled by the subscribers for setting and releasing the switches, and clearing-out signals associated with the o erators circuits to-indicate the desire 0 connected subscribers of disconnection, substantially as described.-

5. In a telephone exchange system a plurality of subscribers-"lines, manual connective terminals therefor, signal devices ass o-.

'ciated therewith and becoming active n response to subscribers" calls, automatic switches containing terminals of the same lines, operators connective. circuits .for con necting a calling'line with an idle switch, means controlled by the subscribers for setting and releasing the switches, and clearing-'out'signals connected with said connec tive circuits, substantially as described.

6. In a telephone exchange system, subscribers lines with manual connective circuits and automatic switches for interconnecting them, each line having an answering terminal manuallyaccessihle only, and one or more calling terminals in the automatic switches only, said switches being subdivided into classes and-groups, certain 'grou s in each class containing multiple termina s for switches of the next class, and the switches of the last class containing the said line terminals, said manual connective circuits adapted 'toinitiate connection between lines through the successive classes,

and means-whereby the continuity of a con-- nection may thereafter be controlled by the subscribers, substantially as described.

7 In a telephone exchange system, subscrlbers lines having manually accessible answering terminals, and automatically accessible calling terminals, two or more sets of link or trunk-circuits each containing an automatic switch fldflflled to be successively operated to reach sai calling terminals, together with operators cord-circuits for interconnecting the first set of links or trunks with calling subscribers lines, and means controlled by the subscribers for setting and rele'asingsaid switches, substantially as described.

8(111 a telephone exchange system, a plu-' "tor switches, substantially as described.

9. In a telephone exchange system, a plurality of subscribers lines, first selector switches in number less than the number of lines, means whereby said switches may be manually switched to be brought under control of calling lines, becoming therebyindividual line switches for the-tlme-being, and auxiliary switches in groups containing the terminals of corresponding groups of trunks,

connector switches connected thereto, and containing terminals of the same subscribers lines in groups, and means whereby the said switches may be controlled through the trunks and theiraccompanying circuits to reach thewanted subscribers lines, and for pur oses of restoration to normal, substantial y as described.

10. The combination in a telephone system of-subscribers lines, a manual switchboard and automatic switches containin respectively answeringand calling terminals for said lines, and operators cord-circuits for interconnecting the calling lines and switches, together with means controlled by the subscribers for both setting and releasing said switches, substantially asdescribed. v

11. A semi-automatic telephone exchange trunking system provided with selectors and connectors responsive to a calling subscriber,

and means by which an operator connects a selector with the line of the calling subscriber before the call can be extended in the direction of the called subscriber.

In testimony whereof I have atfixed' my signature in presence of two witnesses.

f EDWARD E. CLEMENT.

WVitnesses HUGH M. STERLING, JAMES H. MARR.

Copies of this patent may be obtained for five cents cach,.by addressing the Commissioner of Patents, Washington, D. (1. 

